SOLUTION: There are two geometric sequences with 3nd term 5 and 5th term 80. What are the two possible values of the 4rd term?

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Question 927792: There are two geometric sequences with 3nd term 5 and 5th term 80. What are the two possible values of the 4rd term?
Found 2 solutions by stanbon, MathTherapy:
Answer by stanbon(75887)   (Show Source): You can put this solution on YOUR website!
There are two geometric sequences with 3nd term 5 and 5th term 80. What are the two possible values of the 4rd term?
a(3) = ar^2 = 5
a(5) = ar^4 = 80
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Divide and solve for "r"::
r^2 = 16
r = +4 or r = -4
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If r = +4, a = 5/16 and a(4) = (5/16)r^3 = (5/16)*4^3 = 20
If r = -4, a = 80/64 = 5/4 and a(4) = (5/4)(-4)^3 = 5(-16) = -80
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Cheers,
Stan H.
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Answer by MathTherapy(10552)   (Show Source): You can put this solution on YOUR website!

There are two geometric sequences with 3nd term 5 and 5th term 80. What are the two possible values of the 4rd term?
Term 4, or  could be 

You can do the check!! 

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